A zipper, zip, fly or zip fastener, formerly known as a clasp locker, or slide fastener is a commonly used device for binding the edges of an opening of fabric or other flexible material, like on a garment or a bag. It is used in clothing (e.g., jackets and jeans), luggage and other bags, sporting goods, camping gear, and other items.
The bulk of a zipper/zip consists of two rows of protruding teeth, which may be made to interdigitate, linking the rows, carrying from tens to hundreds of specially shaped metal or plastic teeth. These teeth can be either individual or shaped from a continuous coil, and are also referred to as elements. The slider operated by hand, moves along the rows of teeth. Inside the slider is a Y-shaped channel that meshes together or separates the opposing rows of teeth, depending on the direction of the slider's movement.
In general, a zipper represents a small amount of the overall cost of a product. However, if it fails, the entire garment or device may be unusable until the zipper is replaced or repaired. Problems often lie with the slider portion of the zipper. Sliders are typically made of a slide portion and a pull. The user grabs the pull, which is pivotally connected to the slide, and pushes or pulls the slide in one direction or the other to cause the slide to move. Movement of the slide causes the teeth to engage or disengage with each other as the movement occurs. Slides are typically manufactured to include one or more pieces to which the pull is later assembled. Assembly of the pull to the slide is usually accomplished by bending a bridge portion of the slide which is die cast having a gap to create an interlocking engagement between the two components. Other methods require assembly of extra bridge components which may be bent, staked or otherwise secured to the slide. However, these constructions are weak and prone to breakage with repeated use, causing the pull to become separated from the slide.
It has been proposed in the past to form the slide and the pull in a single operation. However, the proposed methods, devices and resulting zipper products have been unable to be produced or are unacceptable to the industry when produced from metal. Producing a metal slider assembly with the pull interlocked with the bridge has proven to be extremely difficult due to the rigid properties of the metal, which makes tool retraction from around the formed part very difficult without modifying the geometry of the part in an undesirable manner.
For example, U.S. Pat. No. 2,736,062 to Scheuermann et al. discloses a method of molding a slide and pull together in a single operation. Scheuermann utilizes four slides that intersect at 45 degree angles with respect to each other. The slides intersect at the bridge and pull portions of the slider assembly with the pull positioned at a vertical right angle with respect to the top surface of the slide. However, this method, as shown in the drawings, requires the inner surfaces of the pull loop and the bridge to include 45 degree or similar angles that form sharp points along the inner surfaces. The sharp points cause stress risers in the part, and the sharp corners wear very quickly causing any surface coatings to be worn away. This results in discoloration of the slide assembly and often results in corrosion of the parts during a washing cycle. In addition, the modified geometry severely limits the movement of the pull within the bridge by reducing the space that the pull has to rotate and slide within the bridge.
U.S. Pat. No. 5,604,962 to Mayerhofer, U.S. Pat. No. 5,698,243 to Wakabayashi, U.S. Pat. No. 4,210,196 to Weiner, and U.K. Patent No 2,220,608 to Liso all show variations of the Scheuermann device, which all require the angles inside of the bridge and the pull to retract the tools. Even though the angles are not depicted in all of the patents, the tooling cannot be retracted through hardened metal, and thus must be there for the tooling to function.
U.S. Pat. No. 2,509,278 to Scheuermann discloses a mold that rotates the pull about its vertical axis to try and eliminate the angles on the inner surface of the pull loop. However, the angles are still required on the inner surface of the bridge, and the difficulty in producing the tools with the precision required for the pull rotation about the vertical axis has proven too costly.
U.S. Pat. No. 4,790,973 to Minami et al. discloses a different method and device for molding slider assemblies. Minami molds the slide first and, once the slide has solidified, a core is partially retracted to form the pull in a secondary molding operation while the slide is still positioned in the mold.
U.S. Pat. No. 5,013,511 to Akashi discloses yet another method and device for forming a zipper slide from metal. Akashi, like Minami, forms the slide portion in a first operation and forms the pull in a secondary operation. However, the pull of Akashi includes a pin which engages the bridge of the slide instead of the loop as disclosed in other prior art.
U.S. Pat. No. 4,985,969 to Terada et al. discloses yet another method and device for forming a zipper slide assembly. Terada forms the pull in combination with an intermediate pull portion with the two portions interlocked with a pin member that is formed within a mold as a secondary operation.
U.K. Patent Application No. 2,289,917 to YKK Corp. discloses a locking slider assembly. The YKK locking slider discloses forming the pull in a separate mold and placing the pull in a secondary mold where the slide is formed around a pin portion of the pull to complete the assembly.
Thus, a need in the art exists for a device and method of forming a slide in combination with a pull, wherein the slide and pull can be formed from metal without the need for modified geometry of the slide assembly, including internal angled surfaces in the bridge and the loop portion of the pull.
The combined slide and pull assembly should satisfy the ergonomic needs that a zipper slide assembly must satisfy in order to achieve acceptance by the end user. This includes providing a slide bridge that includes an internal surface geometry that allows free movement and rotation of the pull. Further, the zipper slide assembly should not require excessive strength to operate or include oversized component parts. Moreover, the zipper slide assembly must assemble together in such a way so as not to detract from the aesthetic appearance of the completed zipper assembly or garment assembly.
Thus, the present invention provides a die cast zipper slide assembly formed in a single operation which overcomes the disadvantages of prior art zipper slide assemblies formed in one or multiple operations. The zipper slide assembly of the present invention not only provides for relative ease in manufacturing, it also permits slides and pulls to be manufactured together without the need to put motion limiting and failure prone angles on the inner surfaces of the bridge and pull loop. The present invention also provides a manufacturing method which utilizes at least one side shifting slide, thereby eliminating the need for slides that interlock at angles and require the part geometry to be modified to accommodate the slide angles.